A keyboard instrument with a top board which can open/close an upper opening has long been known. When a user plays the keyboard instrument, an expansion of sound and a sound quality, etc., during performance can be improved by opening the top board.
For example, Patent No. H09-160560 Gazette disclosed a technology to maintain a state in which the top board is opened by supporting the top board (revolving board) with a prop (bearing bar) located around the upper opening of the keyboard instrument, and close the top board by removing the support of the top board by the prop.
However, in the conventional keyboard instrument mentioned above, when the top board maintains the opening state, opening the top board is required by one hand while operating the prop by the other hand for the prop to support the top board.
Therefore, having to operate two members simultaneously and separately with both hands when the top board is opened is problematic and complicated. In addition, in this case, if the top board is slipped from one hand while the prop is operated by the other hand, there is a risk of pinching the other hand between the top board of the keyboard instrument and the top board.